Accelerator for the vulcanization of rubber



. Patented Mar. 10, 1931' 1 da ormwa, omiaaro;" cananaf assrenon; iar'nsna Assumrnn; nonsense; nxss Acrr-aa cmrcan coun y, or new. YORK,

nnahroa roa'rir voncanl ziarron or nuanna No Drawing. applicatlon lllsllr. t t-Y lenewed Julyl'l, 1930.

The object of this invention isto'pr'ovide I have now? discovereda new. process of a substance for aidin the vulcanization of'gpreparinga hard acetaldehyde-anilineconrubber which will be c eap whileat thesame dens ation product. vI have found that it is time owerful, rapid, non poisonous, ,hard fpossiblefto obtain a hard product suitable 6 but low softening and melting point and j for use asjan accelerator of vulcanization of of a brittle nature so as to allow of easy pul rubberby condensing the anilne and acetalverization and distribution in a rubber mix. dehyde 1n the: presence of acid catalysts.

A further object is to provide in this same Thisi'n'ew. product can be ground to a fine substance a material which will retard the powder and {will not agglomerate after aging of the finished rubber. grinding; it hasexcellent accelerating pro My invention comprises an improved erties. and greatly extends the life of t e product formed by the condensation of acetrubber article in which it is used. It. has aldehyde with amline in the presence of an been proposed to prepare various rubber comacidic catal st and includes a recess of pounding materials such as age resistors, treating rub r, balata, gutta perc a, or simaccelerators and conditioners from-aldehydes ilar material with this improved acetaldeand amines in aqueous acid solutions. In hyde aniline condensation product and vulthese, however, large amounts of acid'are canizing. My invention also includes the present and this not only alters the course of product of the process. This application the reaction and produces a'diiferent type concerns a species of material which is of product, but also serves with the water claimed broadly in an application S. N. to dissolve out certain constituents of the 82,613 filed by me of evendate herewith. mix. The product of this type of high acid The condensation products of acetaldereaction requires neutralization with alkahyde and aniline have been used in various lies and other treatment such as washing forms forsome time as accelerators in the with water to render it suitable for use in art of vulcanizing rubber. These substances rubber. My condensation product is prevary greatly in nature and activity due to pared with acid catalysts in the substantial the varying methods of formation and to the absence of water and has no definite melting many different ratios suggested and empoint. I have found that high acid concenployed between the acetaldehyde and an1l1ne. trations during the preparation of the conost of these substances however are of an lensate has unfavorable effects on the accelundesirable soft pitchy nature being neither erating properties of the product. Furtherhard materials nor free flowing liquids, bemore the water removes constituents which 0111188 f his soft and sticky nature the mateare valuable in accelerating vulcanization. rial is extremely difiicult to handle. Some of One preferred method ofpracticing my inthe so-called hard products are unsuitable in vention is to use an acid zinc salt, such as zinc many cases since the ground particles agchloride, and a mineral acid, such as hydroglomerate on standing. A recently suggested chloric acid, in succession as the acidic cataprocess is a secondary treatment of these soft materials with a further aldehyde addition after a primary condensation as been effected. I have found that such further aldehyde additions are unnecessary and a waste.

' In my U. S. Patent 1,562,146 of Nov. 17, 1925,

I have disclosed and claimed one method of preparing improved condensation products of aldehydes and amines and one application of this process is the formation of an improved acetaldehyde-aniline condensation product.

reaction wherein two moles of acetaldehyde are used to each mole of aniline. I use the zinc chloride first for the purpose of securing a preliminary condensation so as to avoid a violent reaction due to the catalytic effects of the hydrochloric acid when it is added.

The total amount of acidic catalyst used is less than 5% of the weight of the acetaldehyde and aniline so that neutralization of the acid with alkalies is unnecessary. Furthermore the reaction is carried out with essenlysts in an acetaldehyde-aniline condensation are used as the reaction medium and considerable amounts of acid used to dissolve out certain constituents in the reaction product.

I preferably first prepare a catalyst consisting of an addition product of zinc chloride and aniline by mixing these in reacting proportions, e. g. 2 moles'of aniline to one mole of zinc chloride. 0221b. of this zinc chloride-aniline product is then added to. 51.5

pounds of aniline in a jacketed kettle with thorough stirring to prevent the zinc chloride-aniline from settling out. Cooling water is now circulated in the kettle jacket and 50 lbs. acetaldehyde (1.3 pounds excess over the 2 molecular ratio to care for any vaporization loss) are run into the kettle; the pressure in the kettle is allowed to rise to about pounds and the aldehyde addition regulated to maintain this pressure. The addition of the aldehyde takes about 1% hours. The pressure drops to near zero in about minutes after the aldehyde has been added.'

One pound of aqueous hydrochloric acid solution is now added in a period of 10- 15 minutes, with stirring continued as before. Cooling water is still being circulated. Due to the catalytic effect upon adding the acid the kettle temperature rises sharply, reaching'ab'out 8085 C. As soon as this temperature begins to fall showing a completion of the major part of the reaction, the cooling water is shut-oil and the water jacket emptied. Thusthe heat of the reaction is utilized as fully as possible and serves to car ry the reaction to completion. The charge is stirred for about minutes longer 'and then blown out into pans to cool. The prod uct is then ground and dried. The softening point is about 80 C. when tested as described below.

In measuring the hardness of this material I find that a goodindex is the softening point and flowing point. A suitable method for these determinations is described in Allens Commercial Organic Analysis, Fourth Edition, Volume III, pages 76-7 7 for the softening and flowing point of asphalts. Briefly, this consists in spreading some of the ground material on a thin microscope slide placed on a mercury bath heated by a small flame. The temperature rise is adjusted to about 23 C. per minute. The temperature at which individual granules become rounded and take on a deeper color is taken as the softening point; the temperature at which the material spreads on the glass or wets the glass is taken as the flowing point.

I have found that I can repare a'co'mparably hard product with t e zinc chloride alone. In this case the time of treatment is somewhat longer. Whether the catalytic effect shown in my experiments is due to the acidic substances per so, or, to the addition products of these acidic substances with the aniline is immaterial as influencing the scope of this invention. As described in my preferred example the zinc chloride is added to. the batch as a catalyst comprising a zinc Smoked sheet 100 parts by weight Zinc oxide 5 parts by weight Sulphur 5 parts by weight Accelerator 1 part by weight cured at a temperature correspondm to 40 lb? steam pressure gave the following resu ts:

Time of cure Elongation Load at I Load at 700% elong. break 30 9.5 1900 2820 9.0 1700 3480 9.0 2600 3880 75 9.1 3200 3880 90 9.0 2300 2701 I have found that the product prepared as above not only is a good accelerator of the vulcanization of rubber but it also imparts to the rubber very excellent agin properties. The present theory in the art is that theaging of rubber in use is due to an oxidizing action of the air on the rubber. From this standpoint those substances which tend to preserve the rubber,- that is, improve its aging qualities have been designated as antioxidants.

The excellent aging properties of a rubber prepared with the zinc chloride-hydrochloric acid catalyzed product are shown by the following tests made on a rubber prepared as noted above. This rubber was first arti ficially aged by placing in a chamber heated to C. and passing warm fresh air over the rubber. A sample was tested at the end of each day.

Days aged Load at break 3266 lbs/in. 3392 lbs. /in.'- 3303 lbs. /in. 3341 lbs. /in. 3135 lbs. /in. 3155 lbs. /in. 3398 lbs/in. 3449 lbs. /in.

qmvuaoowro acting under essentially with oxygen at 300 pounds per square inch pressure. The results were as follows:

Hours in the Load at break bomb 0 3325 lbs/in. 4s 3125 lbs/in. 72 2625 lbs/in.

This shows excellent aging properties since it has been shown that 10 hours in a bomb under the'above conditions is approximately egauivalent to one year of natural agingierer and Davis, Ind. Eng. Chem.-August 1925) The .age resisting qualitiesv are further brought out in a second bomb test. The

rubber for this test was prepared b utilizing the zinc-chloride-hydrochloric aci catalyzed product as prepared above as the acceleratorantioxidant in the formula:

Smoked sheet 100 parts by weight Zinc oxide 5 parts by weight Sulphur r 5 parts byweight Accelerator antioxidant- 3 parts by weight Cured at temperature of steam at 40 lbs. /in. for 30 minutes. Specimens of this rubber were then a ed in a bomb at C. in an atmosphere 0 oxygen at 300 lbs/in. pressure and the following results obtained.

Hours In the Load at break bomb I O 3100 lbs/in. 48 3100 lbs/in. 7 2 3150 lbs. /in. What I claim is:

an unvulcanized rubber compound, a Vulcan-- izing agent and the product obtained by. reanh drous conditions, aniline and acetaldehydi; in the presence of a small amount of zinc chloride, a small amount of mineral acid, and vulcanizing.

3. A process for treating rubber or similar materials which comprises combining with an unvulcanized rubber compound, a vulcanizing agent and the product obtained by reacting under essentially anhydrous conditions, aniline and acetaldehyde in the presence of a small amount of zinc chloride, a small amount of hydrochloric acid, and vulcanizmg.

4. A rocess'for treating rubber or similar materia s which comprises combining with an unvulcanized rubber compound a vulcanizing agent and the product obtained by re-- acting under essentlally anhydrous conditions, two moles of acetaldehyde and one mole of aniline, a small amount of zinc chloride, 9.

' small amount of a mineral acid,'and vulcanizing. I v

5. A process for treating rubber or similar materials which comprises combinin with an unvulcanized rubber com ound a v canizing agent and the roduct o tained by partially condensing un er essentiall anhydrous conditions two moles of aceta dehyde with one mole of aniline in the ride then completin t e condensation by a small amount of HG and vulcanizing.

vulcanized rubber or similar, material by combining it with a vulcanizing agent and the product obtained by reacting under essentially anhydrous conditions, aniline and acetaldehyde in the presence of a small amount of zinc chloride, and vulcanizing.

7. A vulcanized rubber derived from unvulcanized rubber or similar material by combining it with a vulcanizing a cut and the product obtained by reacting un or essentiall anhydrous conditions, aniline and acetald ehyde in the presence of a small amount of zincchloride, a small amount of mineral acid, and vulcanizing.

resence of zinc chlo- 6. A vulcanized rubber derived from un- 8. A vulcanized rubber derived from unvulcanized rubber or similar material by combining it with a vulcanizing agent and the 7 product obtained 'by reacting under essentiallfi anhydrous conditions, aniline and acetalde zinc c loride, a small amount of hydrochloric acid, and vulcanizing.

lylde in the presence of a small amount of 9. A vulcanized rubber derived from unvulcanized rubber or similar material combined with a vulcanizing agent and the prod duct obtained by reacting under essentially anhydrous conditions, two moles of acetaldehyde and. one mole of aniline, a small amount of zinc chloride, a small amount of a mineral acid, and then vulcanized.

10. A vulcanized rubber derived from unvulcanized rubber or similar material combined with a vulcanizing agent and the product obtained by partially condensing under essentially anhydrous conditions, two moles of acetaldehyde with one mole of aniline in the presence of zinc chloride then completing the condensation by a small amount of HCl, and then vulcanized.

11. Process of treating rubber or similar materials which comprises combining with an unvulcanized rubber compound, a vul canizing agent and an aniline acetaldehyde condensation product containing zinc chloride. I

12. Process of treating rubber or similar materials which comprises combining with an unvulcanized rubber compound, a vulcamz- 'in agent and the condensation product of amline and acetaldehyde containing essentially two moles of acetaldehyde, one mole of anilme and zinc chloride.

Si ed at Perth Amboy, in the county of 5 Mid lesex and State of New Jersey, this 18th day of January, A. D. 1926.

ADRIEN CAMERON. 

